The present invention relates to an electronic wristwatch including a touch sensitive electronic switching circuitry for introducing various commands from the operator and, more particularly, to a touch sensitive electrode structure connected to input terminals of the touch sensitive electronic switching circuitry.
It has been proposed to provide a touch sensitive electronic switching circuitry in an electronic wristwatch because the touch sensitive electronic switching assembly is easy to handle as compared with the mechanical switching structure such as a pushbutton switch or a stem, and the touch sensitive electronic switching circuitry can be incorporated in a C-MOSLSI chip including a time keeping circuit of the electronic wristwatch.
The touch sensitive electronic switching circuitry usually comprises two input terminals, one being connected to a metal rear frame of an electronic wristwatch and the other being connected to a transparent electrode film formed on a front glass window of the electronic wristwatch. In such a system there is a possibility that the front glass window is damaged or becomes dirty since the operator often touches the transparent electrode film formed on the front glass window. The circuit constant of the touch sensitive electronic switching circuitry is difficult to determine, and the insulation must be strictly maintained since the contact resistance is considerably high between the operator's body and the transparent electrode film. Moreover, the front window portion must be made of glass, since other material such as transparent plastics is not suited for the transparent electrode formation.